Closing membranes made of a composite film comprising a support layer made of an aluminum film and a sealing layer connected to the aluminum film for closing a container by sealing the composite film against a circumferential sealing surface of the container or of a cap ring to be connected to the container are known.
For the tight closing of containers made of tinplate or of containers with a cap ring made of tinplate by sealing a closing membrane onto a circumferential sealing surface, the sealing surface had, up until now, to be provided with a heat-sealable coating in order to make the sealing of the closing membrane resistant against temperature fluctuations and pressure fluctuations in the interior of the can.